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This completely DIY casting furnace turned out just great thanks to all the work [Biolit11] put into it along the way. He wanted to replace his older furnace with one that was more efficient, and to that end he built a heat exchanger into the design. This way the exhaust will preheat the intake air.

The furnace itself started with the shell of an old electric water heater. Excluding the design process, the majority of the build involved mold making. For circular parts he’s using quick tube, the paperboard forms used for pouring concrete footings. For more intricate parts he shaped polystyrene. They are layered in place and high-temperature cement is poured to form the permanent parts. After it hardens the polystyrene can be removed in chunks.

The heat exchanger is the part to the left. It includes several wide, flat pipes made of cement for removing the exhaust. Around those pipes a snaking metal chase carries the intake air which picks up the heat as it passes over the exhaust pipes.

For his first run with the new furnace he melted down a bunch of scrap aluminum and poured ingots.

A little dumpster-diving let [Nick Skvarla] build his vacuum form machine for around $5. He pulled a vacuum cleaner out of the trash, which was tossed away because of a broken power plug. He put it into a box which had been sealed with spray foam and used a piece of pegboard for the top side of the enclosure. He takes a piece of 40 mil PETG plastic from the hobby shop and mounts it in a wooden frame. That goes into the oven on broil until the entire sheet is sagging, then onto the vacuum former. Above he’s making forms out of some figurines which he’ll walk you through in the video after the break.

There’s a whole world of manufacturing processes that use these forms as a starting point. What would you use this for?